Note: I didn't introduce the relvar z for the view z = x ^ y because
one extra variable would cause slower assertion evaluation: QBQL
substitutes all the variables with tables from the database definition
file).

Here is the counterexample produced by QBQL:

dx = [p]

1
;

dy = [p]

0
;

dz = [p]
;

y = [p]

0
;

x = [p]

1
;

Therefore, unless we add more constraints the join view is not
updatable.
Received on Tue Sep 01 2009 - 12:31:10 CDT